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Oxygen pt.2: when to say when

Thanks for your feedback! I have noticed several dead cells at times, and could not attribute it to anything particular. Perhaps over-oxygenation was the culprit. I remember reading an article that warned of the dangers of over-oxygenatition (not very accurate since they brewed 2 different styles expecting to achieve the same results) but none the less, it was informative. How and where can one obtain filtered compressed air? This may be my best option when brewing such small batches (7Bbls).

You need to get air from a compressor, which doesn't allow any oil from the compressor into the air and filters it, as well. I've worked in a couple of breweries, which had compressors like these, one had a 10 hl brewhouse, i.e. not much bigger than yours. Maybe someone in your area knows where you can find "food grade" compressed air; sorry, I can't help you there.

Regarding amounts: 25 – 40 liters of air per hl wort. It is pretty much impossible to over-oxygenate with compressed air. It's still good to make sure the temperature is low enough coming out of the heat exchanger before dosing the wort (oxidation from the oxygen in the air will still damage your wort at higher temperatures).

Last edited by crassbrauer; 05-05-2006 at 03:56 PM.
Reason: clarification

Grainger has post compressor filters to remove oil and moisture, i use these to filter the air for my beer pumps, it will save your regulators. Also I have seen some sterile air filters around, what I use are similar to the ones offered on the Beer Beer and More Beer website, they look like White Discs about 3" diameter with hose barbs on each end. I cant remember where I bought them fom because its been a while. I think they claim 99% on air. They might work for you if combined with the oil/moisture filters. Also Brewdr.com has something that might work. I seem to recall that New Belgium did tests with their yeasts and swithched from O2 to compressed air.

So can anyone tell me exactly why it is impossible to over aerate by bubbling air thru the cooled wort? So far, I'm not seeing it. I figure it would still pick up O2 if given a higher dose rate and a longer run time.

And so then, if it's not impossible, you still have the same question that you have with O2... just off by a factor of around 5 (air being 20.9% O2)

Symbiosis

Actually, you already stated the reason why: Only 20 % of the total gas you're trying to dissolve into the wort is oxygen, rather than 100 %, but at roughly the same rate. (I believe there was a thread on the solubility of different gases in wort at some point.) Air is a "mixed gas", too.

Getting down to what happens on a molecular level regarding chemical and physical reactions would belong to the realm of physical chemistry and molecular biology, which I’m not an expert on. However, suffice it to say that oxygen damages any type of living cell in high concentrations. Another example from current research (outside of brewing): Hyperoxia-induced lung injury is a key problem in intensive care units. Patients on ventilators can only breathe oxygen concentrations up to 60 percent for prolonged periods of time. Higher concentrations — though of potential benefit to the body’s organs — lead to severe lung damage (source: Vanderbilt University Medical Center). There’s a saying that goes something like: “Whether a particular compound is poisonous or not, is determined by the dosage”.

This all goes back to the "dawn of time" for prokaryotic life, when we all got mitochondria in a symbiosis that sort of stuck. It would be like the bird on the rhino's back becoming part of the rhino – forever. Up until mitochondria came along oxygen did nothing but damage cells, screwing up DNA, causing mutations in its free-radical form. It was one of the by-products of existence at the time. Then one microbe figured out how to use it to catch an electron at the end of a long electron-transport chain and make lots of energy for itself. It began living in conjunction with another cell and millions and millions of years later: voilą brewers and other large organisms appeared on the earth.

So, you may be wondering at this point: “What is this guy talking about?” My point is that oxygen is a double-edged sword. It is can be harmful, and yet it is essential, kind of like alcohol. It depends on the concentration. Three beers per day (4.0 - 5.0 % abv) is considered healthy (or at least not unhealthy), whereas three glasses of wine or three shots of whiskey per day (the same amount of alcohol yet more concentrated) is not as healthy. The damage caused by alcohol increases dramitically with the concentration.

Did that help? Perhaps I rambled too much. Michael Jackson once said: "One of the things I like about beer is that it makes you digress..."

A question for those using compressed air. How do you measure it? This thread made me want to at least experiment with using compressed air but i am wondering how to measure it. I would be going off a regular psi regulator so litres per minute wouldnt work. I figure since you cant over do the air maybe just go visually and get good saturation without foaming the whole thing all over the place. What do you do, if you use a regulator what do you set it at generally? My flow rate is aprox 40 litres per minute.

Air volume

When I pre purge a lagering tank, and want to know how many liters of co2 comes into the tank / minute, I put a 125 liters plastic bag on the CIP arm and just count the seconds it takes to fill the bag. This easy method might be usefull in measuring air from a compressor if you do not have a flow meter.

You can buy a nice little "oil-less" air compressor from McMaster Carr or any good air compressor supplier can probably get you in the right direction. I would not go with oil removing filters as they can fail and you would risk putting oil into your sterile air lines, if you must go this route then use a food grade oil in your compressor at least in case the filters fail. Then run the air through a 1 micron filter, then carbon (to remove odors), and finally a sterile filter of .45 micron or less. The carbon cartridge seems odd, but if you can stand by your compressor and smell odors that is what is going into the intake of your compressor so it's worth the extra cost to keep that out of your beer. You can run the air through a normal regulator for pressure adjustment, make sure it has a water condensation trap on it to remove water in the lines, and for flow adjustment you can buy a simple "rotameter" air flowmeter (McMaster Carr has these also), it's a plastic tube with a floating disc in it that indicates air flow rate in liters or CFM per minute or per hour depending on how you size it, you can even get them with a built in needle valve for adjustment, they work great. As for over-aerating, if you don't have an O2 meter to check oxygen levels in the wort, you can adjust the air flow so you don't see a lot of foam on top of your beer (or blowoff from the tank vent) but you are still getting a good fermentation...the poor man's method but it worked for us for years.